Well drilling technique and development in coal mine shaft construction

Construction of boreholes is very important for the shaft construction, preparation of development roadway construction and the safety and efficiency of coal mining. So we classify the boreholes in coal mines:those within which worker can carry out underground construction are called wells or shafts, while those which can only be drilled using machines are boreholes. According to their purposes, boreholes can be divided into those for exploration, blast, engineering, engineering-aided, safety and rescue. In addition, the processes of drilling and rock breaking, slag discharge, temporary support, permanent support and deflection control are analyzed. Various rock breaking methods including impact, scraping, cutting, and extrusion methods and their applicable conditions, as well as various slag discharging methods, slurry protecting wall, and temporary supports including drilling with simultaneous casing, permanent supports and the corresponding installation methods including casing and borehole wall are discussed. Then, the swing pendulum angle-drop in large-diameter wellbore drilling, and the measurement while-drilling and the rectification of screw drilling tools in small-diameter wellbore drilling are illustrated. Finally, we forecast the development direction of the drilling technology from the aspects of innovative rock breaking modes, intelligent trajectory control, unmanned drilling equipment, and flexible energy transfer technique.